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Phosphorylated S6K1 is a possible marker for endocrine therapy resistance in hormone receptor-positive breast cancer

Eun-Kyu Kim1, Hyun-Ah Kim, Jae Soo Koh

  • 1Department of Surgery, Korea Cancer Center Hospital, Korea Institute of Radiological and Medical Sciences, Nowon-gu, Seoul, 139-706, Korea.

Breast Cancer Research and Treatment
|December 25, 2010
PubMed

Insights

Phosphorylated S6 kinase 1 (p-S6K1) indicates mammalian target of rapamycin (mTOR) pathway activation. In hormone receptor-positive breast cancer, elevated p-S6K1 expression is a significant predictor of poor survival and potential endocrine therapy resistance.

Area of Science:

  • Oncology
  • Molecular Biology
  • Endocrinology

Background:

  • Cross-talk between estrogen receptor (ER) and mammalian target of rapamycin (mTOR) signaling contributes to endocrine therapy resistance in breast cancer.
  • Phosphorylated S6 kinase 1 (p-S6K1) is a key marker of mTOR pathway activation.

Purpose of the Study:

  • To investigate the prognostic significance of p-S6K1 expression in breast cancer patients.
  • To evaluate the association between p-S6K1 and patient outcomes based on hormone receptor (HR) status.

Main Methods:

  • p-S6K1 expression was assessed in 304 breast cancer tissue samples.
  • Statistical analysis was performed to correlate p-S6K1 levels with overall survival (OS) and breast cancer-specific survival (BCSS).

Main Results:

  • In the hormone receptor-positive (HR+) subgroup (n=197), 35.5% of tumors showed positive p-S6K1 expression.
  • p-S6K1 expression was an independent negative prognostic factor for OS and BCSS in HR+ patients (HR=2.62, P=0.017 and HR=3.25, P=0.020, respectively).
  • No significant association between p-S6K1 expression and survival was observed in the hormone receptor-negative (HR-) group.

Conclusions:

  • p-S6K1 expression serves as a significant adverse prognostic marker in HR+ breast cancer patients.
  • These findings suggest that p-S6K1 may indicate endocrine therapy resistance in HR+ breast cancer.

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